The path leading from the Fishing Hole runs along the south side of the pond above Cliffsburg, and then runs along the top of the cliff on the opposite side of the ravine from Cliffsburg. It leads west along what I suspect is the southern edge of the new region, but I could only travel a short distance before I was blocked by an invisible wall. I've included some screenshots of the path below.

When I hit the invisible wall, I walked to the edge of the cliff to try to get some screenshots of Cliffsburg from the south side of the ravine, but--eep!--I accidentally fell off the cliff. To my surprise, though, I didn't die of adventure, so I was able to take a screenshot from the river below Cliffsburg. It gives you a good sense of how steep the walls of the ravine are. You can also see the watermill again. This was as far as I could swim down the river before hitting the invisible wall.